I think Ewan has a point, why should we be responsible for our pole hose getting dirty? Surely this is down to the manufacturer for not designing a stay clean pole hose.
Even though I agree that there is a need for such an invention, you cannot put the blame with suppliers. You know that the hose is going to get seriously dirty when you are working on a building site, or sandy conditions, and will carry grit up the pole, so it's definitely up to the user to try and avoid that.
It's like saying to a ladder supplier that they should make ladders that will not slip on green decking. That's simply ridiculous. You are responsible to use the ladder (or any tool for that manner) in the way it should be used. Same with the pole, you know it's a limitation of today's water fed poles, and until that is adressed, you as the user should use it in a way that avoids getting too much grit up the pole. A simple way of using that is using a pole hose tidy from Purefreedom, or similar.
Saying that, there is a real need for something that fits on the pole that cleans the pole hose as it goes up the pole.